1. Field of the Invention
The present invention relates to a thermosetting resin composition used for molding a Reflector for an LED, and a Reflector for an LED and an optical semiconductor apparatus using this composition.
2. Description of the Related Art
An optical semiconductor device such as an LED (Light Emitting Diode) has been used as each of various kinds of indicators or light sources for a street display, an automobile lamp, or a residential illumination. As a reflector for an LED material, a large amount of a thermoplastic resin such as a polyphthalamide resin (PPA) is used. Further, an epoxy resin or the like using acid anhydride as a curing agent has been recently used as a reflector material.
Patent Documents 1 to 5 and 7 to 9 have already disclosed that a thermosetting resin such as a silicone resin or an epoxy resin can be used as the Reflector for LED material. Furthermore, a matrix array type reflector is described in Patent Document 6. In Patent Documents 1 to 3, the epoxy resin or the silicone resin is described, but there is no detailed description about the resin itself.
On the other hand, realization of high luminance of an LED device as a backlight in recent liquid crystal television sets or a general illumination light source has rapidly advanced, a demand for reliability or durability of the LED is rigorous in this application, a thermoplastic resin like a liquid crystal polymer or PPA (polyphthalamide) or a thermosetting resin like an epoxy resin conventionally used as a reflector material is severely degraded in an environment where both heat and light are received at the same time, the resin is discolored, reflectance of light is lowered, and hence there arises a problem that such a resin cannot be used as a reflector.
Fused silica or alumina having high purity has been conventionally well known as a filler of this type of reflector resin composition. In general, the reflector must have a whiteness degree that is as high as possible in order to efficiently reflect light. Since the alumina is a very hard material, at the time of kneading a resin composition, the resin composition is blackened and contaminated by the abrasion between alumina and a kneader. Therefore, when a resin composition highly filled with a hard filler such as alumina alone is used, manufacturing a reflector having high reflectance is very difficult. Moreover, since the alumina having high purity is expensive, there is a problem that using this material as a reflector raises a cost.
Additionally, if a thickness of a wall of a reflector formed by using a thermosetting resin composition is thin, there occurs an inconvenience that light emitted from a light emitting device leaks to the outside.